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Prenylation of target GTPases contributes to signaling specificity of Ras-guanine nucleotide exchange factors

T Gotoh1, X Tian, L A Feig

  • 1Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.

The Journal of Biological Chemistry
|August 14, 2001
PubMed

Insights

Ras-GRF1 and Ras-GRF2 are calmodulin-regulated guanine-nucleotide exchange factors (GEFs) that activate Ras proteins. Ras-GRF2

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Protein Biochemistry

Background:

  • Ras-GRF1 and Ras-GRF2 are calmodulin-regulated guanine-nucleotide exchange factors (GEFs).
  • GEFs activate Ras proteins, which are key regulators of cellular processes.
  • Ras-GRF1 and Ras-GRF2 exhibit differential activation of Ras isoforms.

Purpose of the Study:

  • To investigate the differential activation of Ras proteins by Ras-GRF1 and Ras-GRF2.
  • To elucidate the molecular mechanisms underlying the specificity of Ras-GEF interactions.
  • To determine the role of post-translational modifications and lipid modifications in Ras-GEF signaling.

Main Methods:

  • In vivo and in vitro assays to assess guanine-nucleotide exchange activity.
  • Analysis of post-translationally modified and unmodified Ras proteins.
  • Site-directed mutagenesis and chimera analysis of Ras-GRF proteins.
  • Investigation of the impact of different lipid modifications (farnesylation, geranylgeranylation) on Ras-GEF activity.

Main Results:

  • Ras-GRF1 activated both Ha-Ras and R-Ras, while Ras-GRF2 selectively activated Ha-Ras.
  • Ras-GRF2 could not activate processed R-Ras, but activated unprocessed R-Ras and Ha-Ras.
  • Lipid modification of Ras GTPases significantly influenced their responsiveness to Ras-GRF2.
  • A 30-amino acid segment within the catalytic domains of Ras-GRFs mediated lipid recognition.

Conclusions:

  • The lipid moiety attached to GTPases contributes to the signaling specificity of Ras-GEFs.
  • Ras-GRF2's specificity for Ha-Ras over R-Ras is influenced by post-translational and lipid modifications.
  • Understanding these specificities is crucial for deciphering complex Ras-mediated signaling pathways.

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